The invention relates to valved prostheses having flexible polymer leaflets. The invention further relates to improved leaflet designs.
Physicians use a variety of prostheses to correct problems associated with the cardiovascular system, especially the heart. For example, the ability to replace or repair diseased heart valves with prosthetic devices has provided surgeons with a method of treating heart valve deficiencies due to disease and congenital defects. A typical procedure involves removal of the native valve and surgical replacement with a prosthetic heart valve.
Prosthetic heart valve leaflets or occluders perform the function of opening and closing to regulate the blood flow through the heart valve. Typically, heart valve leaflets must either pivot or flex with each cycle of the heart to open and close the valve. Heart valves function as check valves, which open for flow in one direction and close in response to pressure differentials to limit reverse flow.
Prostheses can be constructed from natural materials such as tissue, synthetic materials or a combination thereof. Prostheses formed from purely synthetic materials can be manufactured, for example, from biocompatible metals, ceramics, carbon materials, such as graphite, polymers, such as polyester, and combinations thereof. Heart valve prostheses with purely synthetic materials can be manufactured with rigid occluders (leaflets) that pivot to open and close the valve, or flexible leaflets that flex to open and close the valve.
Although mechanical heart valves with rigid pivoting occluders have the advantage of proven durability through decades of use, they are associated with blood clotting on or around the prosthetic valve and thromboembolism. Blood clotting can lead to acute or subacute dysfunction of the valve. For this reason, patients with mechanical heart valves remain on anticoagulants for as long as the valve remains implanted. Anticoagulants have associated risks and cannot be taken safely by certain individuals.
Heart valve prostheses with flexible leaflets can be constructed with tissue leaflets or polymer leaflets. In prostheses with flexible leaflets, the leaflets are generally designed to approximate natural leaflet function. While the leaflets are flexible, they must have a well defined and stable configuration to properly open and close the valve at each cycle in response to pressure differentials. Also, the leaflets should be durable to provide stable performance over many years of use.
Unlike mechanical valves, tissue based bioprostheses may not require the long term use of anticoagulants due to a lower incidence of thromboembolism. While tissue leaflets have desired flexibility and acceptable hemodynamic performance, tissue leaflets can calcify after implantation, which may result in loss of flexibility or improper closure and/or opening of the valve.
Valve prostheses with polymer leaflets have the potential to overcome the shortcomings of both tissue and mechanical valve designs. The polymers incorporated into heart valve prostheses should provide long term stable function to be suitable alternatives for tissue leaflets or mechanical leaflets.
In a first aspect, the invention pertains to a valved prosthesis including a support structure and a plurality of flexible polymer leaflets connected to the support structure. The support structure has a plurality of commissure supports and scallops between the commissure supports, and the valve has a relaxed state with a lumen that is at least 10 percent of the full open lumen. The flexible polymer leaflets connect to an attachment edge of the leaflet at an angle. In particular embodiments, at a point along the scallops closest to the inflow edge, the flexible polymer leaflets connect to the support structure at an angle toward the inflow edge from about 5 degrees to about 85 degrees relative to a plane normal to the valve axis.
In another aspect, the invention pertains to a valved prosthesis comprising a support structure and at least three flexible polymer leaflets connected to the support structure. The support structure has a plurality of commissure supports and scallops between the commissure supports. The flexible polymer leaflets have a coaptation depth from about 0.3 times the valve radius to about 0.8 times the valve radius.
In another aspect, the invention pertains to a valved prosthesis comprising a support structure and a plurality of flexible polymer leaflets. The support structure has a plurality of commissure supports and scallops between the commissure supports. The flexible polymer leaflets from a valve with a valve height from about one times the valve radius to about 2 times the valve us. The flexible polymer leaflets have leaflet lengths at least about 1 millimeter greater than the valve height.